THE IRRIGATION AGE. 293 



surface in springs, but the great body flows out or is held in under- 

 ground reservoirs at varying depths, and has to be sought for by 

 means of wells, from which ihe water is lifted and forced up to con- 

 siderable elevations by high- duty pumps, where it is distributed, 



The pumps that are in service on the islands are chiefly of Ameri- 

 can build, and are in some instances of large capacity. Their duties 

 range from the small lifts of the centrifugal pumps to those raising 

 12,000,000 gallons per 24 hours. 



The amount of water applied in the irrigation of Hawaiian sugar 

 cane is controlled mainly by the volume of the supply. Concerning 

 the volume that is considered necessary and that is taken as a basis of 

 estimation in calculating the water required by any given plantation 

 and the capacity of the pumps necessary to lift and apply it, reference 

 is had to the data contained in a report on investigations made in 1889 



'by Messrs. J. D. Schuyler and G. F. Allaidt, civil engineers. The 

 data and the views contained in that report were made the basis of 

 operations by the authorities quoted, and they are still the views and 

 represent the practice of those men who were on plantation at the 

 time of the publication of the report in 1889. Other views and other 



' methods are now coming into practice which are based more largely 

 upon the principals set forth in the earlier paragraphs of this report 

 and upon results obtained in actual experiments in irrigation. These 

 will be spoken of later. The report referred to says: 



It seems to be the general practice here [island of Oahu] to irrigate "plant 1 

 cane every three or four days for the first month after planting or unttl it has made 

 a strong growth of root and stalk. After that a watering i? given every seven days 

 for a time, diminishing to one watering every ten days, which is continued for about 

 fifteen months from the time of planting, or until the maturity of the cane. It is 

 customery to eease irrigation from one to three months before cutting. If, as in 

 some districts, the cane did not mature short of eighteen to twenty months from 

 time of planting, the period of irrigation would be from fifteen to eighteen months. 

 In making our estimate we have assumed that fifteen months of irrigation would be 

 the average required for sugar cane on the leeward slopes of this island [Oahu]. 

 Three waterings per month is the least that is considered safe to apply to keep the 

 cane growing without check. In localities corresponding in position and climate to 

 Honouluili it is customary to maintain this periodical irrigation regardless of the 



- rainfall. The rain may at times exceed the quantity applied artificially, but irriga- 

 tion is performed as usual notwithstanding, in order that there shall be no break in 

 the waterings. It seems to be generally understood by all planters that the depth of 

 each watering shall be at least an average of 3 to 4 inches over the whole surface. 



Where the intervals between waterings are ten days and the depth applied is 4 

 inches, 1 cubic foot of water per second will perform a duty of 59.5 acres. With 

 intervals of seven days and the same depth applied, 1 cubic foot per second would 

 irrigate but 41.6 acres, or 55.5 acres if the depth applied is but 3 inches. 



At this place it may be convenient to state, for the use of persons 



who judge by the standard of rainfall, that 1 cubic foot of water per 



; second is equal to a flow of 294,700,032 United States gallons in fifteen 



s months, and that if this volume were applied to 41,6 acres that would 



